The threonine effect on calcium phosphate preparation from a solution containing Ca/P = 1.33 molar ratio

In this study, calcium phosphate materials were prepared by a modified precipitation method using high-speed dispersing equipment. A solution with a Ca/P molar ratio of 1.33 (octacalcium phosphate stoichiometry) was transferred into the reactor vessel with different concentrations of threonine at temperature 97 °C. A white precipitant was collected after the addition of condensed ammonium solution and the samples were subsequently calcined at 900 °C. From the XRD patterns and FT-IR spectra of the uncalcined samples, three phases of octacalcium phosphate (OCP), monetite (DCP) and hydroxyapatite (HA) were obtained. Calcined samples showed two phases of β-tricalcium phosphate (β-TCP) and calcium pyrophosphate (CPP). SEM micrographs showed the different morphology of samples. The specific surface areas (ssa) were 45–53 m2/g for and 5–6 m2/g for calcined samples. From the obtained results, we found that threonine added in various amounts in the initial solution inhibits the formation of HA and consequently creates OCP and DCP.